DEFINITION sn3_appl_abbr()
TYPE =
       ∀c:C
         .∀d:C
           .∀w:T
             .∀i:nat
               .getl i c (CHead d (Bind Abbr) w)
                 →∀v:T
                      .sn3 c (THead (Flat Appl) v (lift (S i) O w))
                        →sn3 c (THead (Flat Appl) v (TLRef i))
BODY =
        assume c: C
        assume d: C
        assume w: T
        assume i: nat
        suppose H: getl i c (CHead d (Bind Abbr) w)
        assume v: T
        suppose H0: sn3 c (THead (Flat Appl) v (lift (S i) O w))
           assume y: T
           suppose H1: sn3 c y
             we proceed by induction on H1 to prove 
                ∀x:T
                  .eq T y (THead (Flat Appl) x (lift (S i) O w))
                    →sn3 c (THead (Flat Appl) x (TLRef i))
                case sn3_sing : t1:T H2:∀t2:T.((eq T t1 t2)→∀P:Prop.P)→(pr3 c t1 t2)→(sn3 c t2) ⇒
                   the thesis becomes 
                   ∀x:T
                     .∀H4:eq T t1 (THead (Flat Appl) x (lift (S i) O w))
                       .sn3 c (THead (Flat Appl) x (TLRef i))
                   (H3) by induction hypothesis we know 
                      ∀t2:T
                        .(eq T t1 t2)→∀P:Prop.P
                          →(pr3 c t1 t2
                               →∀x:T
                                    .eq T t2 (THead (Flat Appl) x (lift (S i) O w))
                                      →sn3 c (THead (Flat Appl) x (TLRef i)))
                       assume x: T
                       suppose H4: eq T t1 (THead (Flat Appl) x (lift (S i) O w))
                         (H5) 
                            we proceed by induction on H4 to prove 
                               ∀t2:T
                                 .(eq T (THead (Flat Appl) x (lift (S i) O w)) t2)→∀P:Prop.P
                                   →(pr3 c (THead (Flat Appl) x (lift (S i) O w)) t2
                                        →∀x0:T
                                             .eq T t2 (THead (Flat Appl) x0 (lift (S i) O w))
                                               →sn3 c (THead (Flat Appl) x0 (TLRef i)))
                               case refl_equal : ⇒
                                  the thesis becomes the hypothesis H3

                               ∀t2:T
                                 .(eq T (THead (Flat Appl) x (lift (S i) O w)) t2)→∀P:Prop.P
                                   →(pr3 c (THead (Flat Appl) x (lift (S i) O w)) t2
                                        →∀x0:T
                                             .eq T t2 (THead (Flat Appl) x0 (lift (S i) O w))
                                               →sn3 c (THead (Flat Appl) x0 (TLRef i)))
                         end of H5
                         (H6) 
                            we proceed by induction on H4 to prove 
                               ∀t2:T
                                 .(eq T (THead (Flat Appl) x (lift (S i) O w)) t2)→∀P:Prop.P
                                   →(pr3 c (THead (Flat Appl) x (lift (S i) O w)) t2)→(sn3 c t2)
                               case refl_equal : ⇒
                                  the thesis becomes the hypothesis H2

                               ∀t2:T
                                 .(eq T (THead (Flat Appl) x (lift (S i) O w)) t2)→∀P:Prop.P
                                   →(pr3 c (THead (Flat Appl) x (lift (S i) O w)) t2)→(sn3 c t2)
                         end of H6
                          assume t2: T
                          suppose H7: (eq T (THead (Flat Appl) x (TLRef i)) t2)→∀P:Prop.P
                          suppose H8: pr2 c (THead (Flat Appl) x (TLRef i)) t2
                            (H9) 
                               by (pr2_gen_appl . . . . H8)

                                  or3
                                    ex3_2 T T λu2:T.λt2:T.eq T t2 (THead (Flat Appl) u2 t2) λu2:T.λ:T.pr2 c x u2 λ:T.λt2:T.pr2 c (TLRef i) t2
                                    ex4_4
                                      T
                                      T
                                      T
                                      T
                                      λy1:T.λz1:T.λ:T.λ:T.eq T (TLRef i) (THead (Bind Abst) y1 z1)
                                      λ:T.λ:T.λu2:T.λt2:T.eq T t2 (THead (Bind Abbr) u2 t2)
                                      λ:T.λ:T.λu2:T.λ:T.pr2 c x u2
                                      λ:T.λz1:T.λ:T.λt2:T.∀b:B.∀u:T.(pr2 (CHead c (Bind b) u) z1 t2)
                                    ex6_6
                                      B
                                      T
                                      T
                                      T
                                      T
                                      T
                                      λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abst)
                                      λb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T (TLRef i) (THead (Bind b) y1 z1)
                                      λb:B
                                        .λ:T
                                          .λ:T
                                            .λz2:T
                                              .λu2:T
                                                .λy2:T.eq T t2 (THead (Bind b) y2 (THead (Flat Appl) (lift (S O) O u2) z2))
                                      λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c x u2
                                      λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2
                                      λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2
                            end of H9
                            we proceed by induction on H9 to prove sn3 c t2
                               case or3_intro0 : H10:ex3_2 T T λu2:T.λt3:T.eq T t2 (THead (Flat Appl) u2 t3) λu2:T.λ:T.pr2 c x u2 λ:T.λt3:T.pr2 c (TLRef i) t3 ⇒
                                  the thesis becomes sn3 c t2
                                     we proceed by induction on H10 to prove sn3 c t2
                                        case ex3_2_intro : x0:T x1:T H11:eq T t2 (THead (Flat Appl) x0 x1) H12:pr2 c x x0 H13:pr2 c (TLRef i) x1 ⇒
                                           the thesis becomes sn3 c t2
                                              (H14) 
                                                 we proceed by induction on H11 to prove 
                                                    eq T (THead (Flat Appl) x (TLRef i)) (THead (Flat Appl) x0 x1)
                                                      →∀P:Prop.P
                                                    case refl_equal : ⇒
                                                       the thesis becomes the hypothesis H7

                                                    eq T (THead (Flat Appl) x (TLRef i)) (THead (Flat Appl) x0 x1)
                                                      →∀P:Prop.P
                                              end of H14
                                              (H15) 
                                                 by (pr2_gen_lref . . . H13)

                                                    or
                                                      eq T x1 (TLRef i)
                                                      ex2_2
                                                        C
                                                        T
                                                        λd:C.λu:T.getl i c (CHead d (Bind Abbr) u)
                                                        λ:C.λu:T.eq T x1 (lift (S i) O u)
                                              end of H15
                                              we proceed by induction on H15 to prove sn3 c (THead (Flat Appl) x0 x1)
                                                 case or_introl : H16:eq T x1 (TLRef i) ⇒
                                                    the thesis becomes sn3 c (THead (Flat Appl) x0 x1)
                                                       (H17) 
                                                          we proceed by induction on H16 to prove 
                                                             (eq
                                                                 T
                                                                 THead (Flat Appl) x (TLRef i)
                                                                 THead (Flat Appl) x0 (TLRef i))
                                                               →∀P:Prop.P
                                                             case refl_equal : ⇒
                                                                the thesis becomes the hypothesis H14

                                                             (eq
                                                                 T
                                                                 THead (Flat Appl) x (TLRef i)
                                                                 THead (Flat Appl) x0 (TLRef i))
                                                               →∀P:Prop.P
                                                       end of H17
                                                       (H_x) 
                                                          by (term_dec . .)
or (eq T x x0) (eq T x x0)→∀P:Prop.P
                                                       end of H_x
                                                       (H18) consider H_x
                                                       we proceed by induction on H18 to prove sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                          case or_introl : H19:eq T x x0 ⇒
                                                             the thesis becomes sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                                (H20) 
                                                                   by (eq_ind_r . . . H17 . H19)

                                                                      (eq
                                                                          T
                                                                          THead (Flat Appl) x (TLRef i)
                                                                          THead (Flat Appl) x (TLRef i))
                                                                        →∀P:Prop.P
                                                                end of H20
                                                                we proceed by induction on H19 to prove sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                                   case refl_equal : ⇒
                                                                      the thesis becomes sn3 c (THead (Flat Appl) x (TLRef i))
                                                                         by (refl_equal . .)
                                                                         we proved 
                                                                            eq
                                                                              T
                                                                              THead (Flat Appl) x (TLRef i)
                                                                              THead (Flat Appl) x (TLRef i)
                                                                         by (H20 previous .)
sn3 c (THead (Flat Appl) x (TLRef i))
sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                          case or_intror : H19:(eq T x x0)→∀P:Prop.P ⇒
                                                             the thesis becomes sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                                (h1) 
                                                                    suppose H20: 
                                                                       eq
                                                                         T
                                                                         THead (Flat Appl) x (lift (S i) O w)
                                                                         THead (Flat Appl) x0 (lift (S i) O w)
                                                                    assume P: Prop
                                                                      (H21) 
                                                                         by (f_equal . . . . . H20)
                                                                         we proved 
                                                                            eq
                                                                              T
                                                                              <λ:T.T>
                                                                                CASE THead (Flat Appl) x (lift (S i) O w) OF
                                                                                  TSort ⇒x
                                                                                | TLRef ⇒x
                                                                                | THead  t ⇒t
                                                                              <λ:T.T>
                                                                                CASE THead (Flat Appl) x0 (lift (S i) O w) OF
                                                                                  TSort ⇒x
                                                                                | TLRef ⇒x
                                                                                | THead  t ⇒t

                                                                            eq
                                                                              T
                                                                              λe:T.<λ:T.T> CASE e OF TSort ⇒x | TLRef ⇒x | THead  t ⇒t
                                                                                THead (Flat Appl) x (lift (S i) O w)
                                                                              λe:T.<λ:T.T> CASE e OF TSort ⇒x | TLRef ⇒x | THead  t ⇒t
                                                                                THead (Flat Appl) x0 (lift (S i) O w)
                                                                      end of H21
                                                                      (H22) 
                                                                         consider H21
                                                                         we proved 
                                                                            eq
                                                                              T
                                                                              <λ:T.T>
                                                                                CASE THead (Flat Appl) x (lift (S i) O w) OF
                                                                                  TSort ⇒x
                                                                                | TLRef ⇒x
                                                                                | THead  t ⇒t
                                                                              <λ:T.T>
                                                                                CASE THead (Flat Appl) x0 (lift (S i) O w) OF
                                                                                  TSort ⇒x
                                                                                | TLRef ⇒x
                                                                                | THead  t ⇒t
                                                                         that is equivalent to eq T x x0
                                                                         by (eq_ind_r . . . H19 . previous)
(eq T x x)→∀P0:Prop.P0
                                                                      end of H22
                                                                      by (refl_equal . .)
                                                                      we proved eq T x x
                                                                      by (H22 previous .)
                                                                      we proved P

                                                                      (eq
                                                                          T
                                                                          THead (Flat Appl) x (lift (S i) O w)
                                                                          THead (Flat Appl) x0 (lift (S i) O w))
                                                                        →∀P:Prop.P
                                                                end of h1
                                                                (h2) 
                                                                   by (pr2_head_1 . . . H12 . .)
                                                                   we proved 
                                                                      pr2
                                                                        c
                                                                        THead (Flat Appl) x (lift (S i) O w)
                                                                        THead (Flat Appl) x0 (lift (S i) O w)
                                                                   by (pr3_pr2 . . . previous)

                                                                      pr3
                                                                        c
                                                                        THead (Flat Appl) x (lift (S i) O w)
                                                                        THead (Flat Appl) x0 (lift (S i) O w)
                                                                end of h2
                                                                (h3) 
                                                                   by (refl_equal . .)

                                                                      eq
                                                                        T
                                                                        THead (Flat Appl) x0 (lift (S i) O w)
                                                                        THead (Flat Appl) x0 (lift (S i) O w)
                                                                end of h3
                                                                by (H5 . h1 h2 . h3)
sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                       we proved sn3 c (THead (Flat Appl) x0 (TLRef i))
                                                       by (eq_ind_r . . . previous . H16)
sn3 c (THead (Flat Appl) x0 x1)
                                                 case or_intror : H16:ex2_2 C T λd0:C.λu:T.getl i c (CHead d0 (Bind Abbr) u) λ:C.λu:T.eq T x1 (lift (S i) O u) ⇒
                                                    the thesis becomes sn3 c (THead (Flat Appl) x0 x1)
                                                       we proceed by induction on H16 to prove sn3 c (THead (Flat Appl) x0 x1)
                                                          case ex2_2_intro : x2:C x3:T H17:getl i c (CHead x2 (Bind Abbr) x3) H18:eq T x1 (lift (S i) O x3) ⇒
                                                             the thesis becomes sn3 c (THead (Flat Appl) x0 x1)
                                                                (H20) 
                                                                   by (getl_mono . . . H . H17)
                                                                   we proved eq C (CHead d (Bind Abbr) w) (CHead x2 (Bind Abbr) x3)
                                                                   we proceed by induction on the previous result to prove getl i c (CHead x2 (Bind Abbr) x3)
                                                                      case refl_equal : ⇒
                                                                         the thesis becomes the hypothesis H
getl i c (CHead x2 (Bind Abbr) x3)
                                                                end of H20
                                                                (H21) 
                                                                   by (getl_mono . . . H . H17)
                                                                   we proved eq C (CHead d (Bind Abbr) w) (CHead x2 (Bind Abbr) x3)
                                                                   by (f_equal . . . . . previous)
                                                                   we proved 
                                                                      eq
                                                                        C
                                                                        <λ:C.C> CASE CHead d (Bind Abbr) w OF CSort ⇒d | CHead c0  ⇒c0
                                                                        <λ:C.C> CASE CHead x2 (Bind Abbr) x3 OF CSort ⇒d | CHead c0  ⇒c0

                                                                      eq
                                                                        C
                                                                        λe:C.<λ:C.C> CASE e OF CSort ⇒d | CHead c0  ⇒c0 (CHead d (Bind Abbr) w)
                                                                        λe:C.<λ:C.C> CASE e OF CSort ⇒d | CHead c0  ⇒c0 (CHead x2 (Bind Abbr) x3)
                                                                end of H21
                                                                (h1) 
                                                                   (H22) 
                                                                      by (getl_mono . . . H . H17)
                                                                      we proved eq C (CHead d (Bind Abbr) w) (CHead x2 (Bind Abbr) x3)
                                                                      by (f_equal . . . . . previous)
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) w OF CSort ⇒w | CHead   t⇒t
                                                                           <λ:C.T> CASE CHead x2 (Bind Abbr) x3 OF CSort ⇒w | CHead   t⇒t

                                                                         eq
                                                                           T
                                                                           λe:C.<λ:C.T> CASE e OF CSort ⇒w | CHead   t⇒t (CHead d (Bind Abbr) w)
                                                                           λe:C.<λ:C.T> CASE e OF CSort ⇒w | CHead   t⇒t (CHead x2 (Bind Abbr) x3)
                                                                   end of H22
                                                                   suppose H23: eq C d x2
                                                                      (H24) 
                                                                         consider H22
                                                                         we proved 
                                                                            eq
                                                                              T
                                                                              <λ:C.T> CASE CHead d (Bind Abbr) w OF CSort ⇒w | CHead   t⇒t
                                                                              <λ:C.T> CASE CHead x2 (Bind Abbr) x3 OF CSort ⇒w | CHead   t⇒t
                                                                         that is equivalent to eq T w x3
                                                                         by (eq_ind_r . . . H20 . previous)
getl i c (CHead x2 (Bind Abbr) w)
                                                                      end of H24
                                                                      consider H22
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) w OF CSort ⇒w | CHead   t⇒t
                                                                           <λ:C.T> CASE CHead x2 (Bind Abbr) x3 OF CSort ⇒w | CHead   t⇒t
                                                                      that is equivalent to eq T w x3
                                                                      we proceed by induction on the previous result to prove sn3 c (THead (Flat Appl) x0 (lift (S i) O x3))
                                                                         case refl_equal : ⇒
                                                                            the thesis becomes sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                               (H_x) 
                                                                                  by (term_dec . .)
or (eq T x x0) (eq T x x0)→∀P:Prop.P
                                                                               end of H_x
                                                                               (H26) consider H_x
                                                                               we proceed by induction on H26 to prove sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                                  case or_introl : H27:eq T x x0 ⇒
                                                                                     the thesis becomes sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                                        we proceed by induction on H27 to prove sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                                           case refl_equal : ⇒
                                                                                              the thesis becomes sn3 c (THead (Flat Appl) x (lift (S i) O w))
                                                                                                 by (sn3_sing . . H6)
sn3 c (THead (Flat Appl) x (lift (S i) O w))
sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                                  case or_intror : H27:(eq T x x0)→∀P:Prop.P ⇒
                                                                                     the thesis becomes sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                                        (h1) 
                                                                                            suppose H28: 
                                                                                               eq
                                                                                                 T
                                                                                                 THead (Flat Appl) x (lift (S i) O w)
                                                                                                 THead (Flat Appl) x0 (lift (S i) O w)
                                                                                            assume P: Prop
                                                                                              (H29) 
                                                                                                 by (f_equal . . . . . H28)
                                                                                                 we proved 
                                                                                                    eq
                                                                                                      T
                                                                                                      <λ:T.T>
                                                                                                        CASE THead (Flat Appl) x (lift (S i) O w) OF
                                                                                                          TSort ⇒x
                                                                                                        | TLRef ⇒x
                                                                                                        | THead  t ⇒t
                                                                                                      <λ:T.T>
                                                                                                        CASE THead (Flat Appl) x0 (lift (S i) O w) OF
                                                                                                          TSort ⇒x
                                                                                                        | TLRef ⇒x
                                                                                                        | THead  t ⇒t

                                                                                                    eq
                                                                                                      T
                                                                                                      λe:T.<λ:T.T> CASE e OF TSort ⇒x | TLRef ⇒x | THead  t ⇒t
                                                                                                        THead (Flat Appl) x (lift (S i) O w)
                                                                                                      λe:T.<λ:T.T> CASE e OF TSort ⇒x | TLRef ⇒x | THead  t ⇒t
                                                                                                        THead (Flat Appl) x0 (lift (S i) O w)
                                                                                              end of H29
                                                                                              (H30) 
                                                                                                 consider H29
                                                                                                 we proved 
                                                                                                    eq
                                                                                                      T
                                                                                                      <λ:T.T>
                                                                                                        CASE THead (Flat Appl) x (lift (S i) O w) OF
                                                                                                          TSort ⇒x
                                                                                                        | TLRef ⇒x
                                                                                                        | THead  t ⇒t
                                                                                                      <λ:T.T>
                                                                                                        CASE THead (Flat Appl) x0 (lift (S i) O w) OF
                                                                                                          TSort ⇒x
                                                                                                        | TLRef ⇒x
                                                                                                        | THead  t ⇒t
                                                                                                 that is equivalent to eq T x x0
                                                                                                 by (eq_ind_r . . . H27 . previous)
(eq T x x)→∀P0:Prop.P0
                                                                                              end of H30
                                                                                              by (refl_equal . .)
                                                                                              we proved eq T x x
                                                                                              by (H30 previous .)
                                                                                              we proved P

                                                                                              (eq
                                                                                                  T
                                                                                                  THead (Flat Appl) x (lift (S i) O w)
                                                                                                  THead (Flat Appl) x0 (lift (S i) O w))
                                                                                                →∀P:Prop.P
                                                                                        end of h1
                                                                                        (h2) 
                                                                                           by (pr2_head_1 . . . H12 . .)
                                                                                           we proved 
                                                                                              pr2
                                                                                                c
                                                                                                THead (Flat Appl) x (lift (S i) O w)
                                                                                                THead (Flat Appl) x0 (lift (S i) O w)
                                                                                           by (pr3_pr2 . . . previous)

                                                                                              pr3
                                                                                                c
                                                                                                THead (Flat Appl) x (lift (S i) O w)
                                                                                                THead (Flat Appl) x0 (lift (S i) O w)
                                                                                        end of h2
                                                                                        by (H6 . h1 h2)
sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
sn3 c (THead (Flat Appl) x0 (lift (S i) O w))
                                                                      we proved sn3 c (THead (Flat Appl) x0 (lift (S i) O x3))
(eq C d x2)→(sn3 c (THead (Flat Appl) x0 (lift (S i) O x3)))
                                                                end of h1
                                                                (h2) 
                                                                   consider H21
                                                                   we proved 
                                                                      eq
                                                                        C
                                                                        <λ:C.C> CASE CHead d (Bind Abbr) w OF CSort ⇒d | CHead c0  ⇒c0
                                                                        <λ:C.C> CASE CHead x2 (Bind Abbr) x3 OF CSort ⇒d | CHead c0  ⇒c0
eq C d x2
                                                                end of h2
                                                                by (h1 h2)
                                                                we proved sn3 c (THead (Flat Appl) x0 (lift (S i) O x3))
                                                                by (eq_ind_r . . . previous . H18)
sn3 c (THead (Flat Appl) x0 x1)
sn3 c (THead (Flat Appl) x0 x1)
                                              we proved sn3 c (THead (Flat Appl) x0 x1)
                                              by (eq_ind_r . . . previous . H11)
sn3 c t2
sn3 c t2
                               case or3_intro1 : H10:ex4_4 T T T T λy1:T.λz1:T.λ:T.λ:T.eq T (TLRef i) (THead (Bind Abst) y1 z1) λ:T.λ:T.λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3) λ:T.λ:T.λu2:T.λ:T.pr2 c x u2 λ:T.λz1:T.λ:T.λt3:T.∀b:B.∀u:T.(pr2 (CHead c (Bind b) u) z1 t3) ⇒
                                  the thesis becomes sn3 c t2
                                     we proceed by induction on H10 to prove sn3 c t2
                                        case ex4_4_intro : x0:T x1:T x2:T x3:T H11:eq T (TLRef i) (THead (Bind Abst) x0 x1) H12:eq T t2 (THead (Bind Abbr) x2 x3) :pr2 c x x2 :∀b:B.∀u:T.(pr2 (CHead c (Bind b) u) x1 x3) ⇒
                                           the thesis becomes sn3 c t2
                                              (H16) 
                                                 we proceed by induction on H11 to prove 
                                                    <λ:T.Prop>
                                                      CASE THead (Bind Abst) x0 x1 OF
                                                        TSort ⇒False
                                                      | TLRef ⇒True
                                                      | THead   ⇒False
                                                    case refl_equal : ⇒
                                                       the thesis becomes 
                                                       <λ:T.Prop>
                                                         CASE TLRef i OF
                                                           TSort ⇒False
                                                         | TLRef ⇒True
                                                         | THead   ⇒False
                                                          consider I
                                                          we proved True

                                                             <λ:T.Prop>
                                                               CASE TLRef i OF
                                                                 TSort ⇒False
                                                               | TLRef ⇒True
                                                               | THead   ⇒False

                                                    <λ:T.Prop>
                                                      CASE THead (Bind Abst) x0 x1 OF
                                                        TSort ⇒False
                                                      | TLRef ⇒True
                                                      | THead   ⇒False
                                              end of H16
                                              consider H16
                                              we proved 
                                                 <λ:T.Prop>
                                                   CASE THead (Bind Abst) x0 x1 OF
                                                     TSort ⇒False
                                                   | TLRef ⇒True
                                                   | THead   ⇒False
                                              that is equivalent to False
                                              we proceed by induction on the previous result to prove sn3 c (THead (Bind Abbr) x2 x3)
                                              we proved sn3 c (THead (Bind Abbr) x2 x3)
                                              by (eq_ind_r . . . previous . H12)
sn3 c t2
sn3 c t2
                               case or3_intro2 : H10:ex6_6 B T T T T T λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abst) λb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T (TLRef i) (THead (Bind b) y1 z1) λb:B.λ:T.λ:T.λz2:T.λu2:T.λy2:T.eq T t2 (THead (Bind b) y2 (THead (Flat Appl) (lift (S O) O u2) z2)) λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c x u2 λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2 λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2 ⇒
                                  the thesis becomes sn3 c t2
                                     we proceed by induction on H10 to prove sn3 c t2
                                        case ex6_6_intro : x0:B x1:T x2:T x3:T x4:T x5:T :not (eq B x0 Abst) H12:eq T (TLRef i) (THead (Bind x0) x1 x2) H13:eq T t2 (THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)) :pr2 c x x4 :pr2 c x1 x5 :pr2 (CHead c (Bind x0) x5) x2 x3 ⇒
                                           the thesis becomes sn3 c t2
                                              (H18) 
                                                 we proceed by induction on H12 to prove 
                                                    <λ:T.Prop>
                                                      CASE THead (Bind x0) x1 x2 OF
                                                        TSort ⇒False
                                                      | TLRef ⇒True
                                                      | THead   ⇒False
                                                    case refl_equal : ⇒
                                                       the thesis becomes 
                                                       <λ:T.Prop>
                                                         CASE TLRef i OF
                                                           TSort ⇒False
                                                         | TLRef ⇒True
                                                         | THead   ⇒False
                                                          consider I
                                                          we proved True

                                                             <λ:T.Prop>
                                                               CASE TLRef i OF
                                                                 TSort ⇒False
                                                               | TLRef ⇒True
                                                               | THead   ⇒False

                                                    <λ:T.Prop>
                                                      CASE THead (Bind x0) x1 x2 OF
                                                        TSort ⇒False
                                                      | TLRef ⇒True
                                                      | THead   ⇒False
                                              end of H18
                                              consider H18
                                              we proved 
                                                 <λ:T.Prop>
                                                   CASE THead (Bind x0) x1 x2 OF
                                                     TSort ⇒False
                                                   | TLRef ⇒True
                                                   | THead   ⇒False
                                              that is equivalent to False
                                              we proceed by induction on the previous result to prove sn3 c (THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3))
                                              we proved sn3 c (THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3))
                                              by (eq_ind_r . . . previous . H13)
sn3 c t2
sn3 c t2
                            we proved sn3 c t2
                         we proved 
                            ∀t2:T
                              .(eq T (THead (Flat Appl) x (TLRef i)) t2)→∀P:Prop.P
                                →(pr2 c (THead (Flat Appl) x (TLRef i)) t2)→(sn3 c t2)
                         by (sn3_pr2_intro . . previous)
                         we proved sn3 c (THead (Flat Appl) x (TLRef i))

                         ∀x:T
                           .∀H4:eq T t1 (THead (Flat Appl) x (lift (S i) O w))
                             .sn3 c (THead (Flat Appl) x (TLRef i))
             we proved 
                ∀x:T
                  .eq T y (THead (Flat Appl) x (lift (S i) O w))
                    →sn3 c (THead (Flat Appl) x (TLRef i))
             by (unintro . . . previous)
             we proved 
                eq T y (THead (Flat Appl) v (lift (S i) O w))
                  →sn3 c (THead (Flat Appl) v (TLRef i))
          we proved 
             ∀y:T
               .sn3 c y
                 →(eq T y (THead (Flat Appl) v (lift (S i) O w))
                      →sn3 c (THead (Flat Appl) v (TLRef i)))
          by (insert_eq . . . . previous H0)
          we proved sn3 c (THead (Flat Appl) v (TLRef i))
       we proved 
          ∀c:C
            .∀d:C
              .∀w:T
                .∀i:nat
                  .getl i c (CHead d (Bind Abbr) w)
                    →∀v:T
                         .sn3 c (THead (Flat Appl) v (lift (S i) O w))
                           →sn3 c (THead (Flat Appl) v (TLRef i))